1. Field of the Invention
The present invention relates generally to a high speed input/output (HSIO) system such as Universal Serial Bus (USB), Serial Advanced Technology Attachment (SATA), Peripheral Component Interconnection express (PCIe), or the like, and more particularly, to a power saving control method for the HSIO system.
2. Description of Related Art
In conventional analog serial high speed input/output (HSIO) systems, the physical layer (PHY) has been designed as a current-drive type. Once an external device is connected to the HSIO and an auto-configuration link is completed, the transmission speed mode of the PHY is set as a fixed value. Therefore, the HSIO system (e.g. USB, SATA, PCIe, or the like) consumes almost the same power within the unit time during data transmission regardless of the data transmission speed. In other words, in the conventional PHY technology, the same drive current is always consumed within the unit time at different data transmission speeds.
In the conventional HSIO technology, adjustment or improvement of the power consumption has been considered regardless of the data rate of the transmitted data. Many high speed transmission applications are starting to use the HSIO systems. However, the new generation HSIO system increases significantly in power consumption. For example, the rated transmission speed of USB3.0 is about 10 times the rated transmission speed of USB2.0 but the power consumption of USB3.0 is about 5 times the power consumption of USB2.0, as shown in Table 1 below. The rated transmission speed of SATA 6G is about twice the transmission speed of SATA 3G but the power consumption of SATA 6G is about 3.5 times the power consumption of SATA 3G, as shown in Table 2 below. The rated transmission speed of PCIe 5G is about twice the rated transmission speed of PCIe 2.5G but the power consumption of PCIe 5G is about 3.75 times the power consumption of PCIe 2.5G, as shown in Table 3 below.
TABLE 1Comparison among USB 1.1 {grave over ( )} USB 2.0 and USB 3.0Max transmissionTransmissionUSB versionspeedpowerUSB 1.1Low speed1.5Mbps≈125kB/s≈15mW/sFull speed12Mbps≈1MB/s≈30mW/sUSB 2.0High speed480Mbps≈40MB/s≈60mW/sUSB 3.0Super speed5Gbps≈400MB/s≈300mW/s[Note]Transmission power values in Table 1 may vary with different PHY design.
TABLE 2Comparison among SATA 1.5 G, SATA 3 G and SATA 6 GMax transmissionTransmissionSATA versionspeedpowerSATA 1.5 G1.5 Gbps ≈150 MB/s ≈70 mW/sSATA 3 G3 Gbps≈300 MB/s≈100 mW/sSATA 6 G6 Gbps≈600 MB/s≈350 mW/s[Note]Transmission power values in Table 2 may vary with different PHY design.
TABLE 3Comparison among PCIe 2.5 G, PCIe 5 G and PCIe 8 GMax transmissionTransmissionPCIe versionspeedpowerPCIe 2.5 G2.5 Gbps ≈250 MB/s ≈80 mW/sPCIe 5 G5 Gbps≈500 MB/s≈300 mW/sPCIe 8 G8 Gbps≈800 MB/s≈450 mW/s[Note]Transmission power values in Table 3 may vary with different PHY design.
The increase in power consumption is more apparent when the HSIO system is used in a low data transmission speed device with higher speed transmission mode. In fact, the actual transmission speed of the transmission interface is usually subjected to the speed of the device itself and the rate of the file data format or function (e.g. MP3 playback or voice recording function). As a result, when the new generation HSIO system is set in the high speed mode, the transmission time is, in many cases, reduced only a little or even is not reduced, but the transmission power consumption increases significantly.
Taking SATA as an example (other HSIO systems have the similar problem), when the actual device data rate makes the high speed SATA 6G unable to bring its advantage of high transmission speed, the interface transmission power consumption of the high speed SATA 6G is much greater than that of the low speed SATA 1.5G. For example, Table 4 is a comparison table showing the comparison between SATA 6G and SATA 1.5G each transmitting same 8G data when the actual max device transmission speed (bottleneck speed) is 200 MB/s.
TABLE 4Comparison between SATA 6G and SATA 1.5 GData amountTransmission(Max Device transmissionTransmissionpowerspeed is 200 MB/s)timeconsumption8 GBSATA 1.5 G53.3 s3.73 WSATA 6 G 40 s 14 W
It can be clear From Table 4 that, if the actual device transmission speed is too low, the interface transmission power consumption of the high speed SATA 6G is much greater than that of the low speed SATA 1.5G. However, the conventional HSIO system does not dynamically switch its transmission speed mode according to the actual transmission speed of the data transmission. The transmission speed mode of the conventional HSIO system is already determined during an initial process at the time an external device is connected to a host. Once determined during the initial process, the transmission speed mode of the conventional HSIO system is fixed. That is, in determining the transmission speed mode of the conventional HSIO system, neither the actual data transmission speed nor the issue of transmission power consumption is considered.